That is actually a sensational deal on the 800. Average price on the 400, but great on the 800. On the cladding, the staining should not be an issue either way. The PVC textured option is nice, just know that it will accumulate more dirt which shows on lighter colors.

So is PVC or Aluminum cladding generally preferred? Is the accumulation of dirt a big issue?

As it pertains to to dirt on cladding, I prefer the kynar finishes on the performance coils. They seem to, in my observations, do a bit better job of shedding dirt.

Depends on whether or not it is an issue in your personal opinion. No big advantage either way, I'd pick based on which appearance you prefer.

+1

Go with whatever look you like at the end of the day.

Do people generally try to negotiate a quote - or is the quote that is provided generally the bottom line?

Most reputable companies give their best price .. Trying to negotiate is sometimes very unfair and makes the process very awkward and can compromise the relationship between you and the company. A little fine tuning is one thing but creating a used car dealership atmosphere is unnecessary.

Depends on the company. Some will have a built in drop, some have specials, and some don't discount.

What does the price feel like to you? Are you getting a good value? What does the company look like on paper? The window is a great unit and well worth the investment. If the company and their work is solid, I think the price is fair.

+1 to WoW's comments. Really depends on how each individual company sets up their pricing structure. At the end of the day, all you are comparing is the final price, whether it was the first one quoted, a special promo, or negotiated. Most companies have at least a small amount of negotiation built in to their regular price.
That said, based on the numbers that you quoted above, I'd be very surprised if you were able to get movement on that Okna pricing. It is very aggressive as is.

Quick follow-up. Is there any difference between windows branded under the Okna name versus the HiMark name? Thanks.

The parent company is the same. The HiMark division is reserved for a specific class of dealer that maintains certain qualifications and standards.

Should I have any concern going with an Okna dealer versus a HiMark?

A good dealer is going to be a good dealer regardless (and vice-versa for a bad one). You'll want to check them out just like you would someone selling any other product.